Given line equation of 2-order:
$$25 x^{2} + 10 x + 16 y^{2} + 8 y + 36 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x + a_{22} y^{2} + 2 a_{23} y + a_{33} = 0$$
where
$$a_{11} = 25$$
$$a_{12} = 0$$
$$a_{13} = 5$$
$$a_{22} = 16$$
$$a_{23} = 4$$
$$a_{33} = 36$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}25 & 0\\0 & 16\end{matrix}\right|$$
$$\Delta = 400$$
Because
$$\Delta$$
is not equal to 0, then
find the center of the canonical coordinate system. To do it, solve the system of equations
$$a_{11} x_{0} + a_{12} y_{0} + a_{13} = 0$$
$$a_{12} x_{0} + a_{22} y_{0} + a_{23} = 0$$
substitute coefficients
$$25 x_{0} + 5 = 0$$
$$16 y_{0} + 4 = 0$$
then
$$x_{0} = - \frac{1}{5}$$
$$y_{0} = - \frac{1}{4}$$
Thus, we have the equation in the coordinate system O'x'y'
$$a'_{33} + a_{11} x'^{2} + 2 a_{12} x' y' + a_{22} y'^{2} = 0$$
where
$$a'_{33} = a_{13} x_{0} + a_{23} y_{0} + a_{33}$$
or
$$a'_{33} = 5 x_{0} + 4 y_{0} + 36$$
$$a'_{33} = 34$$
then equation turns into
$$25 x'^{2} + 16 y'^{2} + 34 = 0$$
Given equation is imaginary ellipse
$$\frac{\tilde x^{2}}{\left(\frac{1}{5 \frac{\sqrt{34}}{34}}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{1}{4 \frac{\sqrt{34}}{34}}\right)^{2}} = -1$$
- reduced to canonical form
The center of canonical coordinate system at point O
(-1/5, -1/4)
Basis of the canonical coordinate system
$$\vec e_1 = \left( 1, \ 0\right)$$
$$\vec e_2 = \left( 0, \ 1\right)$$